1. Field Of The Invention.
The present invention relates to a portable monocular device which, by providing high magnification, is designed for close-up observation.
2. Summary Of The Invention
The portable monocular device of the invention which forms a light and readily transportable optical instrument, is endowed with high magnification (of the order of 18) and makes it possible, better than a strong magnifying glass or a jeweller's eyepiece (instruments which are too short and difficult to fit in the eye) and without having recourse to a binocular device, to observe objects which are substantially invisible to the naked eye and to fix a precise point to be observed (e.g. an insect larvae in agriculture, for identifying it, studying its stage of development, ect. . . . and determining the best treatment times).
According to the invention, the device comprises an elongate housing, open at its ends, on one end of which is fixed an eyepiece and comprising, inside its other end, two biconvex lenses which are of the same power and which are disposed in parallel grooves formed inside the support.
In a particular arrangement, the distance A between the two biconvex lenses is defined by the equality A=(f1)/2 (f1 representing the focal distance of the first lens), this distance A being less than or equal to the diameter of said first lens. The relation between the distance A and the distance B separating the second lens and the eyepiece will then be such that EQU 3A.ltoreq.B.ltoreq.4A.
The monocular device may be formed (except for the optical parts) from a plastic material or a light material, and may have a cylindrical shape or any other suitable shape.
To facilitate cleaning, the eyepiece of the monocular device may advantageously be provided with a plain glass.